1. Field of the Invention
The present invention generally relates to a fluid handling apparatus. More specifically, the invention relates to a fluid handling apparatus for forming a liquid-liquid interface level in a communication portion in which a flow passage is communicated with another flow passage (i.e., in a junction between flow passages).
2. Description of the Prior Art
In recent years, there is known a technique wherein a micro flow passage (a fine flow passage) having a width and depth of about tens to two hundreds micrometers formed in a substrate of a glass or plastic is utilized for carrying out a chemical analysis, a chemical reaction, weighing or the like. A fluid handling apparatus having such a micro flow passage is called microchip. In particular, the fluid handling apparatus is called μ-TAS (Total Analytical System) if it is used for carrying out a chemical analysis, and it is called micro reactor if it is used for allowing a chemical reaction. Since the space of a microchip for carrying out a chemical analysis, a chemical reaction, weighting or the like is very small, the microchip has various advantages, such as the shortening of the time to transport diffuse molecules, and the precise temperature control and weighting.
As such fluid handling apparatuses, there are various apparatuses, each of which has a micro fluid passage having one of various shapes (see Japanese Patent Laid-Open No. 2005-114433 and Japanese Patent Unexamined Publication No. 2003-503715 (National Publication of Translated Version of PCT/US00/18616)). For example, Japanese Patent Laid-Open No. 2005-114433 discloses a fluid handling apparatus capable of precisely metering and quantitatively analyzing a very small amount of sample, such as a protein or nucleic acid, which is required to be analyzed. In addition, Japanese Patent Unexamined Publication No. 2003-503715 discloses a technique for changing the flowability of fluid in capillary to improve the fluid carrying capacity (or the capacity to carry fluid) by devising the surface structure of a flow passage formed in a fluid handling apparatus for carrying out the sampling and purification of a biosubstance, addition and detection of a reagent, and so fourth.
However, in the fluid handling apparatus disclosed in Japanese Patent Laid-Open No. 2005-114433, it is required to operate positive and negative pressures by means of a gas control device in order to exhaust gas from the apparatus, so that there are problems in that the operation of the apparatus is complicated and that the structure of the whole apparatus including the gas control device is complicated and enlarged.
The fluid handling apparatus disclosed in Japanese Patent Unexamined Publication No. 2003-503715 can enhance the flowability of fluid in capillary, but it is not designed to prevent a gas, such as air, existing in the flow passage from remaining therein as bubbles. Therefore, in such a fluid handling apparatus, there are some cases where the bubbles remaining in the flow passage have a bad influence on a chemical analysis, a chemical reaction or the like.